OCTOBER 13, 1899. ] 
and harmonious interpretation by a com- 
parison of its pages with the present condi- 
tion of things. We know infinitely more 
of the history of this earth than we do of 
the history of the sun. Are we then to be 
told that this knowledge, so patiently accu- 
mulated from innumerable observations and 
so laboriously coordinated and classified, is 
to be held of none account in comparison 
with the conclusions of physical science in 
regard to the history of the central luminary 
of our system? These conclusions are 
founded on assumptions which may or may 
not correspond with the truth. They have 
already undergone revision, and they may be 
still further modified as our slender knowl- 
edge of the sun, and of the details of its his- 
tory, is increased by future investigation. 
In the meantime, we decline to accept them 
as a final pronouncement of science on the 
subject. We place over against them the 
evidence of geology and paleontology, and 
affirm that unless the deductions we draw 
from that evidence can be disproved, we are 
entitled to maintain them as entirely borne 
out by the testimony of the rocks. 
Until, therefore, it can be shown that 
geologists and paleontologists have misin- 
terpreted their records, they are surely well 
within their logical rights in claiming as 
much time for the history of this earth as 
the vast body of evidence accumulated by 
them demands. So far as I have been able 
to form an opinion, one hundred millions of 
years would suffice for that portion of the 
history which is registered in the stratified 
rocks of the crust. But if the paleontol- 
ogists find such a period too narrow for 
their requirements, I can see no reason on 
the geological side why they should not be 
at liberty to enlarge it as far as they may 
find to be needful for the evolution of or- 
ganized existence on the globe. As I have 
already remarked, it is not the length of 
time which interests us so much as the de- 
termination of the relative chronology of 
SCIENCE. 
523 
the events which were transacted within 
that time. As to the general succession of 
these events, there can be no dispute. We 
have traced its stages from the bottom of 
the oldest rocks up to the surface of the 
present continents and the floor of the pres- 
ent seas. We know that these stages have 
followed each other in orderly advance, and 
that geological time, whatever limits may 
be assigned to it, has sufficed for the pas- 
sage of the long stately procession. 
We, may, therefore, well leave the dis- 
pute about the age of the earth to the de- 
cision of the future. In so doing, however, 
I should be glad if we could carry away 
from it something of greater service to 
science than the consciousness of having 
striven our best in a barren controversy, 
wherein concession has all to be on one side 
and the selection of arguments entirely on 
the other. During these years of prolonged 
debate I have often been painfully conscious 
that in this subject, as in so many others 
throughout the geological domain, the want 
of accurate numerical data is a serious hin- 
drance to the progress of our science. 
Heartily do I acknowledge that much has 
been done in the way of measurements and 
experiments for the purpose of providing 
a foundation for estimates and deductions. 
But infinitely more remains to be accom- 
plished. The field of investigation is al- 
most boundless, for there is hardly a de- 
partment of geological dynamics over which 
it does not extend. The range of experi- 
mental geology must be widely enlarged, 
until every process susceptible of illustra- 
tion or measurement by artificial means has 
been investigated. Field-observation needs 
to be supplemented where possible by in- 
strumental determinations, so as to be made 
more precise and accurate, and more cap- 
able of furnishing reliable numerical statis-. 
tics for practical as well as theoretical de- 
ductions. 
The subject is too vast for adequate 
